Grounding Sparkplug Wires

[Hooty]

When checking spark, etc., I've always grounded the sprakplug wires to prevent damage to the powerpack. In Sunbird1's "What's wrong" post, in the Johnson & Evinrude Repair Forum, 2KBOAT recommended that Sunbird1 ground the wires to prevent damage to the electrical components. Mr. Joe Reeves responded that grounding isn't necessary. I'm not disputing Mr. Reeves or 2KBOATS but what's correct, grounding or not?<br /><br />c/6<br />Hooty

 

[StillFishin']

Re: Grounding Sparkplug Wires

Good post,Hooty, as I've just resently read about grounding the plugs when your're going to check for spark or else risk blowing the pack. Nothing to offer but very interested in any comments.<br />StillFisin'

 

[roscoe]

Re: Grounding Sparkplug Wires

I have also read several conflicting posts.<br /><br />Hmmm. Perhaps they were referring to different ingnition systems. ???

 

[rodbolt]

Re: Grounding Sparkplug Wires

Hello<br /> I am not going to debate issues. my training in both electronics and auto/marine as well as high voltage transmitters says that if you build a charge to 30,000 volts it really really wants to go someplace. if it back feeds and pops the pack or arcs out of the coil case then oh well. and there is always a safety factor of having all that spark jumping around with no controls. now will it damage the pack or components first time everytime? I doubt it. but the potential is there<br /> good luck keep em grounded and go fish

 

[OBJ]

Re: Grounding Sparkplug Wires

I tend to agree with rodbolt. Can't really say I've seen it in any service manual (I could'a missed it) but just makes sense to give the charge a place to go. Had some radar training in the AF and it was always common place to give an "output" a place to go.

 

[JB]

Re: Grounding Sparkplug Wires

I think I agree with OBJ.<br /><br />The last component in the circuit meant to fire a sparkplug is a transformer (usually called a coil). To feedback a "load" to the primary, current must flow in the secondary circuit, or output. If there is no current in the output circuit, the primary circuit will see a no-load, or "short" condition and may exceed the current supplying ability of a semiconductor driver circuit. . . blowing it. By grounding the plug lead or connecting it to a grounded plug, current is allowed to flow in the secondary circuit.<br /><br />The best "powerpacks" have current limiters in the primary circuit, protecting the drivers.<br /><br />That is of little consequence in a magneto. No semiconductors to pop. The hazard there is using some portion of your body to provide a current path for the secondary circuit. 30,000 to 50,000 volts can give you a start.

 

[AUGIDAWG]

Re: Grounding Sparkplug Wires

So, what happens when you are running at full throttle, and oil foul a plug?<br /><br />Isn't that just like removing the plug cap?<br /><br />If you don't have extra plugs with you, how do you get back to the dock?

 

[JB]

Re: Grounding Sparkplug Wires

A fouled plug flows some current, AUGIDAWG, it just doesn't make an arc. It will not take out the powerpack.<br /><br />It is always a good idea to have a spare set of plugs, and a plug wrench, aboard.

 

[jtexas]

Re: Grounding Sparkplug Wires

My manual (seloc) says ground the wires when you pull 'em, but doesn't give any dire warnings or anything. interesting question, though, if a plug is too fouled to arc, seems like it couldn't pull any current since the circuit would be open? I guess if you let it get that far gone you shouldn't be surprised at whatever problems come up. But at least it's not shocking anybody or starting fires.<br /><br />jw

 

[Hooty]

Re: Grounding Sparkplug Wires

When plugs foul, the firing charge goes to ground through the carbon build up. That's why they don't spark. Same thing when they're flooded. The charge goes to ground through the wet fuel.<br /><br />c/6<br />Hooty